Transcutaneous power and ultrasonic bloodflow velocity sensors.

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Abstract

Ultrasonic flow sensors to monitor blood flow in animals and humans
have been in use for many years. This study draws on the experience of
past research to solve some of the recurring problems found with implanted
sensors. Four areas have been explored, all linked by the contribution
each makes toward the development of an improved blood-flow sensor.
In the first, the use of transcutaneous power to operate an implanted
ultrasonic blood-flow sensor is analyzed. The purpose of such a study is
the total elimination of batteries. The theory of transcutaneous power is
developed from the basic equations of Maxwell and Stefan and a basic efficiency
statement is derived. Design guidelines and graphs are generated
from this statement and basic experiments are conducted to indicate the
validity of the theory. The conclusion is that a properly designed and
applied transcutaneous power-transfer circuit is capable of efficiencies
as high as 90%.
A high-efficiency low-voltage regulator and a low-voltage reference
are developed in the second area. This regulator and reference are compatible
with existing low-voltage implantable circuits intended initially
to be battery powered. The regulator is capable of delivering 2.7 V (two
mercury cells in series) with better than 85% efficiency; the voltage reference
operates from less than 100 uA and has a temperature stability
better than 200 ppm/°C.
The third area details an extensive program involving the design,
fabrication and employment of a discrete-component continuous-wave
implanted ultrasonic doppler blood-flow velocity sensor. The study
includes circuit design and construction, package encapsulation and
extensive clinical results obtained from more than 975 functioning implant
hours with 12 different flow sensors. Among the conclusions derived is
the need for an alternative to batteries as a source of power.
In the fourth area, transcutaneous power, low-voltage regulator
design and the original ultrasonic blood-flow unit are combined in the
first of its kind transcutaneously powered blood-flow velocity sensor.
The details of this sensor are described in addition to the results of
two implants with a prototype unit. The overwhelming conclusion is that
transcutaneous power is an immensely practical alternative to battery
power for certain clinical experiments.

Description

Approved for public release; distribution is unlimited

This thesis document was issued under the authority of another institution, not NPS. At the time it was written, a copy was added to the NPS Library Collection for reasons not now known. It has been included in the digital archive for its historical value to NPS. Not believed to be a CIVINS title.

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